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  • GEOPHYSICS  (755)
  • Engineering  (566)
  • 1985-1989  (1,321)
  • 1975-1979
  • 1965-1969
  • 1989  (1,321)
Collection
Keywords
Publisher
Years
  • 1985-1989  (1,321)
  • 1975-1979
  • 1965-1969
Year
  • 1
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    Global Climate Study (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: The Global Surface Radiation Budget Experiment, which determines if current climate models are accurate, is explained.
    Keywords: GEOPHYSICS
    Type: ASR-250 , NASA-TM-109612 , NONP-NASA-VT-93-190410
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  • 2
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    Iridium in the Vredefort Bronzite Granophyre - Impact melting and limits on a possible extraterrestrial component (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: The Bronzite Granophyre was analyzed for Ir and other elements to examine whether its origin was due to impact melting or conventional igneous assimilation and to search for a possible extraterrestrial component in the melt. No such component is identified. Ir values range from 50-130 pg/g, equivalent to less than 0.05 percent C1 material. Further evidence against an extraterrestrial source of siderophiles are the low Ir/Au ratios and the absence of systematic correlations between Ir and other elements. However, the Granophyre is significantly enriched in Ir over other Vredefort granitic rocks, implying a fundamental difference between them. Geochemical mixing models indicate that the Ir observed in the Granophyre can be supplied from high-Ir local shales and quartzites during an impact melting event. The results are consistent with the view that the Granophyre is an impact melt and that Vredefort is an impact structure.
    Keywords: GEOPHYSICS
    Type: Lunar and Planetary Science Conference; Mar 14, 1988 - Mar 18, 1988; Houston, TX; United States
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  • 3
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    The planning and execution of ER-2 and DC-8 aircraft flights over Antarctica, August and September 1987 (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: The significant ozone loss in the lower stratosphere over Antarctica during recent austral springs was studied by instrumented ER-2 and DC-8 aircraft. Data on the homogeneous gas composition, polar stratospheric clouds, and on tracers for dynamic motion are provided. The mission design is described, the aircraft and their payloads are documented, and the flight tracks are specified.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 11181-11
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  • 4
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    The role of NASA in geodynamics research - Past and future (1989)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: NASA participation in geophysics and geodynamics studies is addressed. Recent NASA activities in these areas are reviewed and plans and suggestions for the future are outlined. International cooperative activities in geophysics and geodynamics are briefly examined. New technologies that will be applied are considered.
    Keywords: GEOPHYSICS
    Type: EOS (ISSN 0096-3941); 70; 713
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  • 5
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    A study of the effect of synoptic scale processes in GCM modelling (1989)
    In:  CASI
    Details
    Publication Date: 2019-08-14
    Description: Research was conducted to help modeling groups at NASA to develop better weather forecasting and general circulation models (GCM) for activities relating to the meteorological uses of satellite data. The focus was on the physical processes that were being simulated by models: radiative effects and latent heat release associated with clouds; orographic influences; and heat transfer at the ocean and ice surfaces. An attempt was made to deduce the role of diabatic heating in North Atlantic cyclogenesis and in the global heat budget. Inferences were made in four studies: heat budget statistics from GCM assimilations; dynamics of north Atlantic cyclones; Cage-type energy budget calculations; and grid scale cloud formation. Mechanisms that were responsible for the variability and structure of the atmospheric on a hemispheric scale were studied by a hybrid of statistical analysis and theoretical modeling. Variability and structure are both related to synoptic scale processes through baroclinic and barotropic energy transformations.
    Keywords: GEOPHYSICS
    Type: NASA-CR-184804 , NAS 1.26:184804
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  • 6
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    Comparison of satellite-derived dynamical quantities for the stratosphere of the Southern Hemisphere (1989)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: As part of the international Middle Atmosphere Program (MAP), a project was instituted to study the dynamics of the Middle Atmosphere in the Southern Hemisphere (MASH). A pre-MASH workshop was held with two aims: comparison of Southern Hemisphere dynamical quantities derived from various archives of satellite data; and assessing the impact of different base-level height information on such derived quantities. The dynamical quantities examined included geopotential height, zonal wind, potential vorticity, eddy heat and momentum fluxes, and Eliassen-Palm fluxes. It was found that while there was usually qualitative agreement between the different sets of fields, substantial quantitative differences were evident, particularly in high latitudes. The fidelity of the base-level analysis was found to be of prime importance in calculating derived quantities - especially the Eliassen-Palm flux divergence and potential vorticity. Improvements in base-level analyses are recommended. In particular, quality controls should be introduced to remove spurious localized features from analyses, and information from all Antarctic radiosondes should be utilized where possible. Caution in drawing quantitative inferences from satellite data for the middle atmosphere of the Southern Hemisphere is advised.
    Keywords: GEOPHYSICS
    Type: NASA-CP-3044 , L-16593 , NAS 1.55:3044 , Workshop on the Middle Atmosphere in the Southern Hemisphere; Apr 14, 1986 - Apr 17, 1986; Williamsburg, VA; United States
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  • 7
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    Two-Dimensional Intercomparison of Stratospheric Models (1989)
    In:  CASI
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    Publication Date: 2019-08-13
    Description: A detailed record is provided for the examination of fundamental differences in photochemistry and transport among atmospheric models. The results of 16 different modeling groups are presented for several model experiments.
    Keywords: GEOPHYSICS
    Type: NASA-CP-3042 , REPT-89B00192 , NAS 1.55:3042 , Sep 11, 1988 - Sep 16, 1988; Virginia Beach, VA; United States
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  • 8
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    Major wildfires at the Cretaceous-Tertiary boundary (1989)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: K-T boundary (KTB) clays from five sites are enriched in soot and charcoal by factors of 100-1000 over Cretaceous levels, apparently due to a global fire. The soot profile nearly coincides with the Ir profile, implying that the fire was triggered by the impact. Much or all of the fuel was biomass, as indicated by the presence of retene and by the C isotopic composition. The amount of elemental C at the KTB (0.012 g/sq cm) is very large, and requires either that most of the Cretaceous biomass burned down or that the soot yield was higher than in small fires. At undisturbed sites, soot correlates tightly with Ir, As, Sb, and Zn. Apparently soot and Ir-bearing ejecta particles coagulated in the stratosphere and then scavenged additional chalcophiles from the hydrosphere. In view of this coagulation, the K-T fire would only slightly prolong the period of darkness and cold caused by impact ejecta.
    Keywords: GEOPHYSICS
    Type: 1988 BAAS Mason Meeting of the Royal Astronomical Society; Sept. 6, 1988; Oxford
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  • 9
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    The low energy atmospheric antiproton albedo (1989)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: The flux of albedo antiprotons in the 100-1000 MeV kinetic energy range produced by the cosmic ray primaries in the atmosphere is calculated. It is shown that this is not a significant background to measurements of the low energy anti-proton cosmic ray flux.
    Keywords: GEOPHYSICS
    Type: AIP Conference on Cosmic Abundances of Matter; Sept. 7-9, 1988; Minneapolis, MN; United States
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  • 10
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    Remote sensing of the earth's atmosphere by infrared absorption spectroscopy - An update of the ATMOS program (1989)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The NASA's Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment was designed to address the requirements of the remote sensing of atmospheric composition on a four-dimensional basis (latitude, longitude, altitude, and time), necessary for understanding and predicting the effect of changes on the chemical balance of the atmosphere. This paper describes the ATMOS program, overviews the ATMOS instrument and its performance, and presents the results obtained during its first flight as part of the Spacelab 3 Space Shuttle mission (April 29 through May 6, 1985). Also discussed are prospects for further missions.
    Keywords: GEOPHYSICS
    Type: Advanced Optical Instrumentation for Remote Sensing of the Earth''s Surface from Space; Apr 27, 1989 - Apr 28, 1989; Paris; France
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  • 11
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    The interdisciplinary role of space geodesy; Proceedings of the International Workshop, Erice, Italy, July 23-29, 1988 (1989)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The current status of space geodesy and research plans for the 1990s are discussed in reviews and reports. Sections are devoted to the short-term and long-term dynamics of the solid earth, interactions between space geodesy and other disciplines and programs (geodynamics, earth structure, ocean physics, atmosphere and climate, planetary science, and fundamental physics), instrumentation, data analysis, reference coordinate systems, and education. Also provided are overviews of the French, ESA, and NASA geodetic research programs and descriptions of the Soviet Glonass navigation satellites, the WEGENER/MEDLAS observation program, and the Lageos II laser-ranging satellites. Diagrams, graphs, maps, and tables of numerical data are provided.
    Keywords: GEOPHYSICS
    Type: Intl. Workshop on the Interdisciplinary Role of Space Geodesy; Jul 23, 1988 - Jul 29, 1988; Erice; Italy
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  • 12
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    Middle Atmosphere Program. Handbook for MAP, volume 28 (1989)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Extended abstracts from the fourth workshop on the technical and scientific aspects of MST (mesosphere stratosphere troposphere) radar are presented. Individual sessions addressed the following topics: meteorological applications of MST and ST radars, networks, and campaigns; dynamics of the equatorial middle atmosphere; interpretation of radar returns from clear air; techniques for studying gravity waves and turbulence; intercomparison and calibration of wind and wave measurements at various frequencies; progress in existing and planned MST and ST radars; hardware design for MST and ST radars and boundary layer/lower troposphere profilers; signal processing; and data management.
    Keywords: GEOPHYSICS
    Type: NASA-CR-184972 , NAS 1.26:184972 , MAP-HANDBOOK-28 , Workshop on Technical and Scientific Aspects of MST Radar; Nov 28, 1988 - Dec 02, 1988; Kyoto; Japan
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  • 13
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    Strain accumulation and surface deformation along the San Andreas, California (1989)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The goal of this project remains to be the achievement of a better understanding of the regional and local deformation and crustal straining processes in western North America, particularly the effect of the San Andreas and nearby faults on the spatial and temporal crustal deformation behavior. Construction of theoretical models based on the mechanics of coupled elastic plate/viscoelastic foundation and large scale crack mechanics provide a rational basis for the interpretation of seismic and aseismic anomalies and expedite efforts in forecasting the stability of plate boundary deformations. In the present period, special focus is placed on the 3-D effect of irregular fault locked patches on the ground measured deformation fields. Specifically, use is made of a newly developed 3-D boundary element program to analyze the fault slip and vertical ground motion in the Parkfield area on the San Andreas.
    Keywords: GEOPHYSICS
    Type: NASA-CR-185893 , NAS 1.26:185893
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  • 14
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    Middle Atmosphere Program. Handbook for MAP, volume 27 (1989)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The proceedings are presented from the MAP program of July 1988. It is intended to be a quick synopsis of the symposium. General topics include: New International Equatorial Observatory; Dynamics of the Middle Atmosphere in Winter (DYNAMICS); Global Budget of Stratospheric Trace Constituents (GLOBUS); Gravity Waves and Turbulence in the Middle Atmosphere Program (GRATMAP); Middle Atmosphere Electrodynamics (MAE); Winter in Northern Europe (WINE); Atmospheric Tides Middle Atmosphere Program (ATMAP); and many others.
    Keywords: GEOPHYSICS
    Type: NASA-CR-184979 , NAS 1.26:184979 , MAP-HANDBOOK-27 , PB89-206510 , COSPAR Sym. 6, The Middle Atmosphere After MAP; Jul 18, 1988 - Jul 23, 1988; Espoo; Finland*Estonia|Jul 17, 1988 - Jul 31, 1988|MAP Steering Committee Meeting Intern. Workshop on Noctil ucent Clouds; Jul 18, 1988; Tallin; Estonia
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  • 15
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    Parallel electric fields in a simulation of magnetotail reconnection and plasmoid evolution (1989)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Properties of the electric field component parallel to the magnetic field (E sub parallel) in a three-dimensional MHD simulation of plasmoid formation and evolution in the magnetotail in the presence of a net dawn-dusk magnetic field component were observed. Particularly emphasized was the spatial location of E(sub parallel), the concept of a diffusion zone and the role of E(sub parallel) in accelerating electrons. A localization of the region of enhanced E(sub parallel) in all space directions with a strong concentration in the z direction was found. This region was identified as the diffusion zone, which plays a crucial role in reconnection theory through the local break-down of magnetic flux conservation. The presence of B(sub y) implies a north-south asymmetry of the injection of accelerated particles into the near-earth region, if the net B(sub y) field is strong enough to force particles to follow field lines through the diffusion region. It is estimated that for a typical net B(sub y) field this should affect the injection of electrons into the near-earth dawn region, so that precipitation into the Northern (Southern) Hemisphere should dominate for duskward (dawnward) net B(sub y). In addition, a spatial clottiness of the expected injection of adiabatic particles which could be related to the appearance bright spots in auroras was observed.
    Keywords: GEOPHYSICS
    Type: DE89-012622 , LA-UR-89-1592 , CONF-8903131-1 , Chapman Conference on the Physics of Magnetic Flux Ropes; Mar 27, 1989 - Mar 31, 1989; Hamilton; Bermuda
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  • 16
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    Wave emissions from planetary magnetospheres (1989)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: An important development in the Earth magnetosphere was the discovery of the boundary of the plasma sheet and its apparent role in the dynamics of the magnetotails. Three instabilities (negative energy mode, counterstreaming, and the Buneman instability) were investigated through analytical and numerical studies of their frequency and growth rate as a function of the angle of propagation.
    Keywords: GEOPHYSICS
    Type: NASA-CR-185435 , NAS 1.26:185435
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  • 17
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    Laser ranging data analysis (1989)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Results of the near real-time analysis of Lageos laser ranging data are reported. The data was analyzed in terms of range bias, time bias, and internal precision; and estimates for the Earth orientation parameters X sub p, Y sub p, and UT1 are obtained. The results of these analyses are reported in a variety of formats. Sample copies of the weekly summaries from the second half of 1988 are included along with an annotated distribution list of the weekly summaries. Annual summaries for 1987 and 1988 are also included.
    Keywords: GEOPHYSICS
    Type: NASA-CR-184847 , NAS 1.26:184847
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  • 18
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    Scene identification probabilities for evaluating earth radiation measurements (1989)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Alongtrack data from the Earth Radiation Budget Experiment (ERBE) satellite are used here to derive scene identification probabilities empirically. These error probabilities are shown to be functions of view zenith angle and scene type, but not of other parameters such as solar zenith angle and relative azimuth angle, except in the sunglint region. The standard deviations of the resulting errors in radiative fluxes are also presented.
    Keywords: GEOPHYSICS
    Type: ; 7 p.|Conference on Probability and Statistics in the Atmospheric Sciences; Oct 02, 1989 - Oct 06, 1989; Monterey, CA; United States
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  • 19
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    The interpretation of crustal dynamics data in terms of plate motions and regional deformation near plate boundaries (1989)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: A particularly detailed set of observations in the vicinity of an intraplate, thrust earthquake (M 7.4) in Argentina, indicate a cyclic pattern of deformation very similar to that reported previously for interplate earthquakes. This deformation cycle, which may be characteristic of many seismically active areas, consists of: (1) steady strain accumulation, possibly punctuated by strain reversals; (2) coseismic strain release; (3) a period of continued strain release due to afterslip (persisting for perhaps a year or so); and (4) rapid postseismic strain accumulation which decreases exponentially and grades into steady strain accumulation. Deformation associated with three earthquakes in the U.S. (1940, M7.1 Imperial Valley California; 1964, M8.4 Alaska; 1959, M7.5 Hebgen Lake, Montana) are interpreted in light of this general earthquake cycle and are used to investigate the mechanics of strain release for these events. These examples indicate that large postseismic movements can occur for strike-slip, thrust, and normal fault events, and both viscoelastic relaxation and postseismic after-slip must be incorporated in models of earthquake related deformation. The mechanics of the strain release process revealed by these examples has implications for estimating earthquake repeat times from geodetic observations near active faults.
    Keywords: GEOPHYSICS
    Type: NASA-CR-180077 , NAS 1.26:180077
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  • 20
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    Middle Atmosphere Program. Handbook for MAP. Volume 31: Reference models of trace species for the COSPAR international reference atmosphere (1989)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: A set of preliminary reference atmosphere models of significant trace species which play important roles in controlling the chemistry, radiation budget, and circulation patterns of the atmosphere were produced. These models of trace species distributions are considered to be reference models rather than standard models; thus, it was not crucial that they be correct in an absolute sense. These reference models can serve as a means of comparison between individual observations, as a first guess in inversion algorithms, and as an approximate representation of observations for comparison to theoretical calculations.
    Keywords: GEOPHYSICS
    Type: NASA-CR-188625 , NAS 1.26:188625 , Jul 18, 1988; Espoo; Finland
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  • 21
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    Middle Atmosphere Program. Handbook for MAP. Volume 30: International School on Atmospheric Radar (1989)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Broad, tutorial coverage is given to the technical and scientific aspects of mesosphere stratosphere troposphere (MST) meteorological radar systems. Control issues, signal processing, atmospheric waves, the historical aspects of radar atmospheric dynamics, incoherent scatter radars, radar echoes, radar targets, and gravity waves are among the topics covered.
    Keywords: GEOPHYSICS
    Type: NASA-CR-188623 , NAS 1.26:188623 , Nov 24, 1988 - Nov 28, 1988; Kyoto; Japan
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  • 22
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    Calculating the electromagnetic field on the earth due to an electrodynamic tethered system in the ionosphere (1989)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A method is presented for calculating the electromagnetic wave field on the earth's surface associated with the operation of an electrodynamic tethered satellite system of constant or slowly varying current in the upper ionosphere. The wave field at the ionospheric boundary and on the earth's surface is obtained by numerical integration. The results suggest that the ionospheric waves do not propagate into the atmosphere and that the image of the Alfven wings from a steady-current tether should be greatly broadened on the earth's surface.
    Keywords: GEOPHYSICS
    Type: AIAA PAPER 89-1553 , International Conference on Tethers in Space - Toward Flight; May 17, 1989 - May 19, 1989; San Francisco, CA; United States
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  • 23
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    Sources of clasts in terrestrial impact melts - Clues to the origin of LKFM (1989)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Low-K Fra Mauro (LKFM) 'basalt', which is found exclusively as an impact melt rock, cannot be modeled geochemically from its clast population or from any combination of known pristine lunar rock types. To clarify clast/melt relationships, a study was made of impact melt rocks from Mistastin Lake crater, Labrador, where there are only three target rocks: anorthosite, quartz monzonite, and granodiorite. Feldspar compositions in these rocks define distinct fields on the An-Ab-Or ternary diagram, making it possible to identify the source of each feldspar clast. Clasts in the Mistastin impact melts do not reflect the abundance of target rocks melted during the impact. The abundance of anorthosite in the clast population varies from 34 to 100 percent compared to a relatively constant value of 65 percent calculated to be in the melt matrix. Therefore the clasts appear to be derived predominantly from material relatively far removed from the zone of impact melting. Melt-matrix composition is dictated strictly by the composition of the target materials within a small radius around and below the point of impact. This suggests that the LKFM composition was derived from a lower crustal source.
    Keywords: GEOPHYSICS
    Type: Lunar and Planetary Science Conference; Mar 14, 1988 - Mar 18, 1988; Houston, TX; United States
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  • 24
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    The delineation and interpretation of the earth's gravity field (1989)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: In an attempt to understand the mechanical interaction of a growing lithosphere containing fracture zones with small and large scale mantle convection, which gives rise to geoid anomalies in oceanic regions, a series of fluid dynamical experiments is in progress to investigate: (1) the influence of lithosphere structure, fluid depth and viscosity field on the onset, scale, and evolution of sublithospheric convection; (2) the role of this convection in determining the rate of growth of lithosphere, especially in light of the flattening of the lithosphere bathymetry and heat flow at late times; and (3) combining the results of both numerical and laboratory experiments to decide the dominate factors in producing geoid anomalies in oceanic regions through the thermo-mechanical interaction of the lithosphere and subjacent mantle. The clear existence of small scale convection associated with a downward propagating solidification front (i.e., the lithosphere) and a larger scale flow associated with a discontinuous upward heat flux (i.e., a fracture zone) has been shown. The flows exist simultaneously and each may have a significant role in deciding the thermal evolution of the lithosphere and in understanding the relation of shallow mantle convection to deep mantle convection. This overall process is reflected in the geoid, gravity, and topographic anomalies in the north-central Pacific. These highly correlated fields of intermediate wavelength (approx. 200 to 2000 km) show isostatic compensation by a thin lithosphere for shorter (less than or equal to approx. 500 km), but not the longer, wavelengths. The ultimate, dynamic origin of this class of anomalies is being investigated.
    Keywords: GEOPHYSICS
    Type: NASA-CR-185333 , NAS 1.26:185333
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  • 25
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    Studies of regional and global tectonics and the rotation of the earth using very-long baseline interferometry (1989)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Progress in the areas of data analysis, atmospheric delay calibration and software conversion is reported. Over 800 very long baseline interferometry (VLBI) experiments were analyzed in the last 6 months. Reprocessing of the Mark III VLBI data set is almost completed. Results of analysis of the water-vapor radiometer (WVR) data were submitted and a preprint of a related paper is attached. Work on conversion of the VLBI analysis software from HP1000 to Unix based workstations is continuing.
    Keywords: GEOPHYSICS
    Type: NASA-CR-185059 , NAS 1.26:185059
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  • 26
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    Plate motions and deformations from geologic and geodetic data (1989)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The very long baseline interferometry (VLBI) measurements made in the western U.S. since 1979 provide discrete samples of the temporal and spatial deformation field. The interpretation of the VLBI derived rates of deformation requires an examination of geologic information and more densely sampled ground based geodetic data. Triangulation and trilateration data measured on two regional networks, one in the central Mojave Desert and one in the Coast Ranges east of the San Andreas fault, were processed. At the spatial scales spanned by these local geodetic networks, auxiliary geologic and geophysical data were utilized to examine the relation between measured incremental strain and the accommodation of strain seen in local geologic structures, strain release in earthquakes, and principal stress directions inferred from in situ measurements. VLBI data was also processed from stations distributed across the Pacific-North America plate boundary zone in the western U.S. The VLBI data were used to constrain the integrated rate of deformation across portions of the continental plate boundary in California and to provide a tectonic framework to interpret regional geodetic and geologic studies.
    Keywords: GEOPHYSICS
    Type: NASA-CR-184987 , NAS 1.26:184987
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  • 27
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    Improvements in the Global Reference Atmospheric Model and comparisons with a global 3-D numerical model (1989)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The status of the Global Reference Atmospheric Model (GRAM) and the Mars Global Reference Atmospheric Model (MARS-GRAM) is reviewed. The wavelike perturbations observed in the Viking 1 and 2 surface pressure data, in the Mariner 9 IR spectroscopy data, and in the Viking 1 and 2 lander entry profiles were studied and the results interpreted.
    Keywords: GEOPHYSICS
    Type: NASA-CR-184947 , NAS 1.26:184947
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  • 28
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    A visiting scientist program in atmospheric sciences for the Goddard Space Flight Center (1989)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A visiting scientist program was conducted in the atmospheric sciences and related areas at the Goddard Laboratory for Atmospheres. Research was performed in mathematical analysis as applied to computer modeling of the atmospheres; development of atmospheric modeling programs; analysis of remotely sensed atmospheric, surface, and oceanic data and its incorporation into atmospheric models; development of advanced remote sensing instrumentation; and related research areas. The specific research efforts are detailed by tasks.
    Keywords: GEOPHYSICS
    Type: NASA-CR-183421 , NAS 1.26:183421
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    Nitric acid oxide mixing ratio measurements using a rocket launched chemiluminescent instrument (1989)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: A total of 18 rocket launched parachute borne nitric oxide instruments were launched from 1977 to 1985. A very precise instrument for the measurement of the nitric oxide mixing ratio was fabricated. No changes were made in the main body of the instruments, i.e., things associated with the reaction volume. Except for the last 4 launches, however, it did not yield the required absolute values that was hoped for. Two major problems were encountered. First, the wrong choice of the background calibration gas, nitrogen, caused the first 10 data sets to be too low in the absolute mixing ratio by nearly the order of 2 to 5 ppbv. The error was realized, and air was substituted for the bias gas measurement. Second, in the desire to extend the measurement to higher altitudes, the problem of contaminating the inlet flow tube with ozone from the reagent gas was encountered. The ozone valve was opened too early in the flight and this caused the pressure in the reaction volume to exceed the pressure at the flow tube entrance, permitting the ozone to migrate backwards. This problem was restricted to an altitude above 45 km.
    Keywords: GEOPHYSICS
    Type: NASA-CR-182957 , NAS 1.26:182957
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    Workshop on the Archean Mantle (1989)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The Workshop on the Archaen mantle considers and discusses evidence for the nature of earth's Archaen mantle, including its composition, age and structure, influence on the origin and evolution of earth's crust, and relationship to mantle and crustal evolution of the other terrestrial planets. The summaries of presentations and discussions are based on recordings made during the workshop and on notes taken by those who agreed to serve as summarizers.
    Keywords: GEOPHYSICS
    Type: NASA-CR-186156 , NAS 1.26:186156 , LPI-TR-89-05 , Jan 11, 1989 - Jan 13, 1989; Houston, TX; United States
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    Group-kinetic theory and modeling of atmospheric turbulence (1989)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: A group kinetic method is developed for analyzing eddy transport properties and relaxation to equilibrium. The purpose is to derive the spectral structure of turbulence in incompressible and compressible media. Of particular interest are: direct and inverse cascade, boundary layer turbulence, Rossby wave turbulence, two phase turbulence; compressible turbulence, and soliton turbulence. Soliton turbulence can be found in large scale turbulence, turbulence connected with surface gravity waves and nonlinear propagation of acoustical and optical waves. By letting the pressure gradient represent the elementary interaction among fluid elements and by raising the Navier-Stokes equation to higher dimensionality, the master equation was obtained for the description of the microdynamical state of turbulence.
    Keywords: GEOPHYSICS
    Type: NASA-CR-183776 , NAS 1.26:183776
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    Progress in the Determination of the Earth's Gravity Field (1989)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Topics addressed include: global gravity model development; methods for approximation of the gravity field; gravity field measuring techniques; global gravity field applications and requirements in geophysics and oceanography; and future gravity missions.
    Keywords: GEOPHYSICS
    Type: NASA-CR-185721 , NAS 1.26:185721 , REPT-397 , Sep 13, 1988 - Sep 16, 1988; Fort Lauderdale, FL; United States
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    Laboratory simulations of energetic atom interactions occurring in low earth orbit (1989)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The Space Shuttle flights provided the first significant data base on the environment experienced by a large space structure operating in LEO. A number of interesting and unanticipated effects were observed, including material erosion induced by ambient oxygen atoms, the visible Shuttle glow occurring above surfaces exposed to the ram flow, and large near-field perturbations and variability in the gaseous neutral and plasma environment about the Shuttle. This paper provides a brief overview of these observations and their phenomenological interpretation, and then discusses laboratory approaches to their investigation. The emphasis is on the state of the art in the development of energetic oxygen atoms sources and the variety of experiments presently being performed with such devices.
    Keywords: GEOPHYSICS
    Type: Intl. Symposium on Rarefied Gas Dynamics: Space-Related Studies; Jul 10, 1988 - Jul 16, 1988; Pasadena, CA; United States
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    Geodynamics applications of spaceborne laser ranging (1989)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The Geodynamics Laser Ranging System (GLRS) is a spaceborne laser ranging instrument being developoed by NASA as a facility instrument for the Earth Observing System (EOS). GLRS is to be used to study regional and local crustal movements. It is designed to make highly precise range measurements to retroreflector targets located in geophysically interesting sites. Using a two-color ranging scheme, absolute range accuracies of several mm are expected. Simulations based on this accuracy and the EOS orbital parameters show that length of the intersite baseline between retroreflectors can be determined to several mm accuracy at distances from a few km to several hundred km with several passes of GLRS range data collected over a few-day interval. Short-arc techniques are used to minimize the effects of gravity field and other force model uncertainties. Relative heights can be determined to sub-cm accuracy over comparable distances.
    Keywords: GEOPHYSICS
    Type: Laser Applications in Meteorology and Earth and Atmospheric Remote Sensing; Jan 16, 1989 - Jan 18, 1989; Los Angeles, CA; United States
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    Middle Atmosphere Program. Handbook for MAP, volume 29. Part 1: Extended Abstracts, International Symposium on Solar Activity Forcing of the Middle Atmosphere. Part 2: MASH Workshop (1989)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The proceedings of the symposium is presented. Eight different sessions were presented: (1) Papers generally related to the subject; (2) Papers on the influence of the Quasi Biennial Oscillation; (3) Papers on the influence of the solar electromagnetic radiation variability; (4) Papers on the solar wind and high energy particle influence; (5) Papers on atmospheric circulation; (6) Papers on atmospheric electricity; (7) Papers on lower ionospheric variability; and (8) Solar posters, which are not included in this compilation.
    Keywords: GEOPHYSICS
    Type: NASA-CR-186005 , NAS 1.26:186005 , MAP-HANDBOOK-29-PT-1/2 , Apr 03, 1989 - Apr 08, 1989; Liblice; Czechoslovakia* United States|Apr 01, 1986; Williamsburg, VA; United States
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    New estimates of area and mass for the North American tektite strewn field (1989)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A revised estimate is given for the total mass of the North American tektite material, which is based on a concept of patches or rays of distribution rather than on a continuous tektite and microtektite blanket. This concept yields a total mass of about 3 x 10 to the 14th g, which is less than a third of previous estimates. The shape of the North American tektite strewn field is in agreement with other tektite strewn fields.
    Keywords: GEOPHYSICS
    Type: Lunar and Planetary Science Conference; Mar 14, 1988 - Mar 18, 1988; Houston, TX; United States
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    Heterogeneous dissemination of projectile materials in the impact melts from Wabar crater, Saudi Arabia (1989)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The initial observations of Spencer (1933) that two distinct impact melts coexist at the 90-m-diameter Wabar crater, Saudi Arabia, is confirmed. A dark or 'black' melt contains on the order of 4 percent meteoritic contamination, while the transparent or 'white' melt contains less than 1 percent. The Fe/Ni ratios in both varieties exhibit considerable scatter on electron-microprobe scales, akin to those reported by others for metal spherules in the black melt. If the meteoritic component is subtracted, both melts are chemically very similar. Clasts engulfed by the Wabar melts were investigated also, as they represent the progenitor lithologies from which the melts formed. Bulk compositions for these clasts reveal subtle differences in modal feldspar content within the quartz-rich Wabar target. Both melts require that a minimum of two target lithologies be present in the Wabar melt zone.
    Keywords: GEOPHYSICS
    Type: Lunar and Planetary Science Conference; Mar 14, 1988 - Mar 18, 1988; Houston, TX; United States
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    Evolution of southern Caribbean plate boundary, vicinity of Trinidad and Tobago (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The tectonic evolution of the southeastern corner of the Caribbean is examined, using field data from the El Pilar fault zone of Trinidad and offshore seismic data. It is found that the dominant process in the region's tectonic evolution is strike-slip motion on at least five major fault systems in a 250-km wide east-west-trending plate-boundary zone extending from Grenada in the north to the Orinoco River in the south. The geological effects of this evolution over the past 30 m y are described.
    Keywords: GEOPHYSICS
    Type: American Association of Petroleum Geologists, Bulletin (ISSN 0149-1423); 73; 490-509
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    The ultraviolet radiation environment of Antarctica - McMurdo Station during September-October 1987 (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Daily data from the Nimbus-7 TOMS were combined with a model of atmospheric radiative transfer to compute the time evolution of ultraviolet irradiance, at wavelengths from 290 to 350 nm, incident on McMurdo Station during September-October 1987. Large changes in column ozone occur as the polar vortex moves over the site. This is accompanied by correspondingly large variations in UV radiation at the earth's surface. At a wavelength near 305 nm, the irradiance in early October exceeds values appropriate to an unperturbed ozone layer by a factor of 5-6. As December 21 approaches, the noontime UV irradiance increases, irrespective of changes in ozone.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 8491-849
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    Inference of stratospheric aerosol composition and size distribution from SAGE II satellite measurements (1989)
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    Publication Date: 2019-07-12
    Description: A method for inferring stratospheric aerosol composition and size distribution from the water vapor concentration and aerosol extinction measurements obtained in the Stratospheric Aerosol and Gas Experiment (SAGE) II and the associated temperature from the NMC. The aerosols are assumed to be sulfuric acid-water droplets. A modified Levenberg-Marquardt algorithm is used to determine model size distribution parameters based on the SAGE II multiwavelength aerosol extinctions. It is found that the best aerosol size information is contained in the aerosol radius range between about 0.25 and 0.80 micron.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 8435-844
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    SAGE II aerosol correlative observations - Profile measurements (1989)
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    Publication Date: 2019-07-12
    Description: Profiles of the aerosol extinction measurements from the Stratospheric Aerosol and Gas Experiment (SAGE) II are compared with profiles from five correlative experiments between November 1984 and July 1986. The correlative profiles were derived from six-channel dustsonde measurements and two-wavelength lidar backscatter data. The correlation between the dustsonde- and lidar-derived measurements and the SAGE II data is good, validating the SAGE II lower stratospheric aerosol extinction measurements.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 8353-836
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    Hot ion plasmas from the cloud of neutral gases surrounding the Space Shuttle (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Large intensities of hot positive ions are observed out to distances of several hundred meters from the Space Shuttle with a plasma analyzer on a small free-flying satellite, the Plasma Diagnostics Package. This ion plasma is inferred to be generated by the charge exchange of ionospheric O+ ions with a large cloud of water molecules from the Space Shuttle. The measured ion density ranges from about 30 to 10,000 H2O+ ions/cu cm. A model for the water vapor cloud provides the basis for density estimates as high as 10 to the 9th H2O molecules/cu cm at a distance of 50 m from the Space Shuttle. Thus, the Space Shuttle possesses a substantial coorbiting atmosphere.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 3721-372
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    The neutral E region zonal winds during intense postmidnight diffuse aurora - Response to observed particle fluxes (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Zonal winds associated with diffuse auroras were simulated using observed fluxes of electron precipitation and a high-resolution time-dependent numerical model described by Waltershcheid et al. (1985). A very strong dynamically unstable E region jet is simulated for an electric field of 50 mV/m, and the results suggest a connection with omega band. These zonal winds are not as strong as those reported by Lyons and Walterscheid (1985), but are much stronger (by a factor of 3 or greater) than the E region winds simulated by Fuller-Rowell (1985). The effects of large-scale cross-arc winds were simulated to evaluate their effect; it is shown that strong cross-arc winds are required to prevent the formation of a strong E zonal jet. The results agree qualitatively with radar observations of zonal winds by Johnson et al. (1987).
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 3703-371
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    The thermal catastrophe model of substorms (1989)
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    Publication Date: 2019-07-12
    Description: Equations are presented for the physical mechanisms involved in the resonant absorption of Alfven waves in the plasma sheet boundary layer. It is shown that energy absorbed by the plasma-sheet particles is a function of the central plasma sheet temperature. The heating curve, when coupled with convective transport, yielded an equation of state for the steady state plasma sheet, whose solution has the form of a mathematical catastrophe. The master equation includes dynamic terms describing the transition across the thermal catastrophe, making it possible to evaluate the time scale for the catastrophe to occur.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 6581-659
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    Entry and acceleration of He(+) in the low latitude boundary layer (1989)
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    Publication Date: 2019-07-12
    Description: AMPTE/CCE He(+) and H(+) observations in the magnetosphere, low latitude boundary layer, and magnetosheath reveal that cold plasmaspheric He(+) distributions from the outer magnetosphere convect into the low latitude boundary layer. In the boundary layer, the cold He(+) is accelerated and heated to a few keV. The data are resolved in sufficient detail to show that the process of pickup of the cold He(+) distribution in the boundary layer H(+) flow may not be adequate to explain the observed He(+) distributions in the boundary layer.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 16; 751-754
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    Electron velocity space hole modes and narrowband electrostatic noise in the distant tail (1989)
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    Publication Date: 2019-07-12
    Description: Narrowband electrostatic noise (NEN) is frequently observed upstream of the slow shocks in the distant tail. It is suggested that NEN represents a nonstandard plasma wave mode which results from a hole in the low energy electron velocity distribution. A very simple model which plausibly indicates how a hole might be formed by the interaction of the electrons with the slow shock is presented. The hole mode is destabilized by a positive slope in the parallel electron distribution and/or by a weak beam of energetic ions which escape upstream from the slow shock.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 16; 747-750
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    Simultaneous observations of electrostatic oxygen cyclotron waves and ion conics (1989)
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    Publication Date: 2019-07-12
    Description: A sounding rocket launched to 927 km apogee during an auroral substorm encountered regions of large quasi-static electric fields (not greater than 400 mV/m), ion conics (up to 700 eV maximum observed energy), and fluctuating electric fields near the oxygen cyclotron frequency. Since the fluctuating electric fields frequently exhibited spectral peaks just above the local oxygen cyclotron frequency, and since the fluctuating electric fields were linearly polarized, they are positively identified as electrostatic oxygen cyclotron waves (EOCW). The maximum amplitude of the EOCW was about 5 mV/m rms. The EOCW closely correlated with the presence of ion conics. Because of the relatively low amplitude of the EOCW and their relatively low coherence, it cannot be concluded that they are solely responsible for the production of the ion conics.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 16; 739-742
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    Three-dimensional spherical models of convection in the earth's mantle (1989)
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    Publication Date: 2019-07-12
    Description: Three-dimensional spherical models of mantle convection in the earth reveal that upwelling cylindrical plumes and downwelling planar sheets are the primary features of mantle circulation. Thus subduction zones and descending sheetlike slabs in the mantle are fundamental characteristics of thermal convection in a spherical shell and are not merely the consequences of the rigidity of the slabs, which are cooler than the surrounding mantle. Cylindrical mantle plumes that cause hot spots such as Hawaii are probably the only form of active upwelling and are therefore not just secondary convective currents separate from the large-scale mantle circulation.
    Keywords: GEOPHYSICS
    Type: Science (ISSN 0036-8075); 244; 950-955
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    Ion conics and counterstreaming electrons generated by lower hybrid waves in the earth's magnetosphere (1989)
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    Publication Date: 2019-07-12
    Description: The exotic phenomenon of energetic ion-conic and counterstreaming electron formation by lower hybrid waves along discrete auroral field lines in the earth magnetosphere is considered. Mean-particle calculations, plasma simulations, and analytical treatments of the acceleration processes are described. It is shown that, in the primary auroral electron-beam region, lower hybrid waves could be an efficient mechanism for the transverse heating of H (+) and O(+) ions of ionospheric origin, as well as for the field-aligned heating of the ambient electrons leading to coincident counterstreaming electron distributions. For O(+) ions to be energized by such a wave-particle interaction process, however, some sort of preheating mechanism is required.
    Keywords: GEOPHYSICS
    Type: IEEE Transactions on Plasma Science (ISSN 0093-3813); 17; 186-195
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    Solitary waves in mantle plumes (1989)
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    Description: Numerical calculations in two dimensions show that solitary wave disturbances can propagate along thermal plumes in a homogeneous, viscous fluid with a thermally activated rheology similar to the mantle. Comparison of the numerical results with analytic results from an idealized two-fluid model indicates that the two-fluid model can be applied to solitary waves in the thermally activated plume. A two-fluid model of solitary waves on cylindrical conduits is accordingly applied to mantle plumes to estimate the propagation speeds, time durations, and pulse lengths of solitary waves in mantle plumes as a function of background mantle viscosity, plume flux, plume density deficit, plume viscosity, and the volume of material transported by the solitary wave. It is inferred that mantle plumes may be eposodic via solitary waves and that these disturbances might account for observed 0(10 m.y.) variations in the durations and spacings of episodes of enhanced hotspot volcanic activity. Solitary waves in mantle plumes could be generated by interactions among plumes and between plumes and the large-scale, time-dependent mantle circulation.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 9523-953
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    Effective elastic thicknesses of the lithosphere and mechanisms of isostatic compensation in Australia (1989)
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    Publication Date: 2019-07-12
    Description: The isostatic compensation of Australia is investigated using an isostatic model for the Australian lithosphere that assumes regional compensation of an elastic plate which undergoes flexure in response to surface and subsurface loading. Using the coherence between Bouguer gravity and topography and two separate gravity/topography data sets, it was found that, for the continent as a whole, loads with wavelengths above 1500 km are locally compensated. Loads with wavelengths in the range 600-1500 km are partially supported by regional stresses, and loads with wavelengths less than 600 km are almost entirely supported by the strength of the lithosphere. It was found that the predicted coherence for a flexural model of a continuous elastic plate does not provide a good fit to the observed coherence of central Australia. The disagreement between model and observations is explained.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 9353-936
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    Dynamic mixing in magma bodies - Theory, simulations, and implications (1989)
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    Description: The magma-mixing process is different from the mantle mixing process in that the mixing components of magma are dynamically active, with the melt density depending strongly on composition. This paper describes simulations of time-dependent variable-viscosity double-diffusive convection which were carried out to investigate quantitatively the mixing dynamics of magma in melt-dominated magma bodies. Results show that the dynamics of double-diffusive convection can impart complex patterns of composition, through time and space. The mixing time depends nonlinearly on many factors, including heat flux driving convection, the rate of diffusion of chemical species, the relative importance of thermal and chemical buoyancy, the viscosities of the mixing components, and the shape of the magma body.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 9215-923
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    Tectonic evolution of the Tobago Trough forearc basin (1989)
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    Publication Date: 2019-07-12
    Description: The histories of configurational changes and sedimentation in the Tobago Trough, which is a modern bathymetric forearc basin of the Lesser Antilles island arc, were investigated using marine seismic data from the Tobago Trough. Special attention is given to two tectonic problems. The first is the evolution of the southeastern corner of the Caribbean as related to the finding that the early forearc basins had substantially different configurations from that of the modern forearc basin. The second is the interaction between the forearc basin and the accretionary prism within the Lesser Antilles system. It is pointed out that Miocene and younger features of the Tobago Trough might reflect a superposition of tectonism associated with the development of the Neogene Lesser Antilles arc on an older arc system.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 2913-293
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    Ion beam generation at the plasma sheet boundary layer by kinetic Alfven waves (1989)
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    Publication Date: 2019-07-12
    Description: A two-dimensional quasi-linear numerical code was developed for studying ion beam generation at the plasma sheet boundary layer by kinetic Alfven waves. The model assumes that the central plasma sheet is the particle source, and that the last magnetic field lines on which kinetic Alfven waves exist and diffusion occurs can be either open or closed. As the possible source for the excitement of the kinetic Alfven waves responsible for ion diffusion, the resonant mode conversion of the surface waves to kinetic Alfven waves is considered. It is shown that, depending on the topology of the magnetic field at the lobe side of the simulation system, i.e., on whether field lines are open or closed, the ion distribution function may or may not reach a steady state.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 10047-10
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    Suprathermal electrons at earth's bow shock (1989)
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    Description: Results are presented on electron measurements near the earth's bow shock, carried out with the fast-plasma experiments on ISEE 1 and 2, with emphasis placed on the suprathermal population of electrons present near the earth's bow shock. The pattern found for the suprathermal electrons at the bow shock suggests that a portion of the solar wind electron population is commonly accelerated to relatively high energy as the solar wind convects across quasi-perpendicular portions of the bow shock. The results are interpreted in terms of the global magnetic field geometry of the bow shock environment.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 10011-10
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    Taylor instability in rhyolite lava flows (1989)
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    Publication Date: 2019-07-12
    Description: A refined Taylor instability model is developed to describe the surface morphology of rhyolite lava flows. The effect of the downslope flow of the lava on the structures resulting from the Taylor instability mechanism is considered. Squire's (1933) transformation is developed for this flow in order to extend the results to three-dimensional modes. This permits assessing why ridges thought to arise from the Taylor instability mechanism are preferentially oriented transverse to the direction of lava flow. Measured diapir and ridge spacings for the Little and Big Glass Mountain rhyolite flows in northern California are used in conjunction with the model in order to explore the implications of the Taylor instability for flow emplacement. The model suggests additional lava flow features that can be measured in order to test whether the Taylor instability mechanism has influenced the flows surface morphology.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 5815-582
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    Carbon-14 in methane sources and in atmospheric methane - The contribution from fossil carbon (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Measurements of carbon-14 in small samples of methane from major biogenic sources, from biomass burning, and in clean air samples from both the Northern and Southern hemispheres reveal that methane from ruminants contains contemporary carbon, whereas that from wetlands, peat bogs, rice fields, and tundra, is somewhat depleted in carbon-14. Atmospheric (C-14)H4 seems to have increased from 1986 to 1987, and levels at the end of 1987 were 123.3 + or - 0.8 percent modern carbon in the Northern Hemisphere and 120.0 + or - 0.7 percent modern carbon in the Southern Hemisphere.
    Keywords: GEOPHYSICS
    Type: Science (ISSN 0036-8075); 245; 286-290
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    The magnetospheric response to 8-minute period strong-amplitude upstream pressure variations (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: This paper documents a series of brief, strong (delta p/p = 1), dynamic pressure oscillations that occurred in the region upstream of the earth's bow shock during a period of radial interplanetary magnetic field. The analyzed set of oscillations, which may be either intrinsic solar wind or bow shock-related phenomena, recur approximately every 8-10 min, and their magnetic field signatures occur nearly simultaneously over great distances transverse to the earth-sun line. The pressure oscillations appear to drive tailward-moving magnetopause surface wavelets. In turn, the surface wavelets can be identified as hydromagnetic waves with strong compressional components in the outer magnetosphere and as quasi-periodic variations in electron precipitation and high-latitude ground pulsations. Observations by spacecraft in the outer dayside magnetosphere are used to predict geosynchronous and subsolar magnetic field strengths, the location of the subsolar magnetopause, the solar wind dynamic pressure, and variations in the energetic magnetospheric ion flux.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 2505-251
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    Magnetosphere-thermosphere coupling - An experiment in interactive modeling (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The present use of the Rice convection model to investigate the electrodynamic coupling of the thermosphere to the inner magnetosphere encompasses the effects of EUV-driven and convection-driven neutral winds under quasi-equilibrium conditions. Convection-driven winds are included self-consistently and interactively; a steady-state wind parameterization is written analytically in terms of the electrostatic potential, which is in turn included in a closed-loop calculation for the electric potential itself. The simulations conducted show that, as the neutral system approaches a quasi-equilibrium state, the neutral winds play a much more significant role.
    Keywords: GEOPHYSICS
    Type: AD-A206881 , AFOSR-TR-89-0467 , Journal of Geophysical Research (ISSN 0148-0227); 94; 2631-264
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    The coalescence of magnetic flux ropes and reconnection in the magnetotail (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 2471-248
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    Ion diffusion coefficients from resonant interactions with broadband turbulence in the magnetotail (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 2484-249
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  • 62
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    Charge balancing of trivalent trace elements in olivine and low-Ca pyroxene - A test using experimental partitioning data (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Charge-balancing substitution mechanisms are determined for the incorporation of the trivalent cations Al and Sc in low-Ca pyroxene and Al, Sc, Yb, and Cr in olivine. In low-Ca pyroxene, the substitution mechanism is determined by evaluating covariations of trivalent trace cations with Si, Mg, Fe, and Ca. In olivine, substitution mechanisms are determined by comparing the observed compositional dependence of partitioning to the compositional dependence theoretically expected for each substitution reaction. A realistic equilibrium constant is formulated for trace element exchanges between olivines, low-Ca pyroxenes, and melt, making possible improved modeling of the variations of trace element partitioning with temperature and phase composition.
    Keywords: GEOPHYSICS
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 53; 643-648
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  • 63
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    River Valley pluton, Ontario - A late-Archean/early-Proterozoic anorthositic intrusion in the Grenville Province (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: This paper presents Nd, Sr, and Pb isotopic data indicating a late-Archean/early-Proterozoic age for the River Valley anorthositic pluton of the southwestern Grenville Province of Sudbury, Ontario. Pb-Pb isotopic data on 10 whole-rock samples ranging in composition from anorthosite to gabbro yield an age of 2560 + or - 155 Ma. The River Valley pluton is thus the oldest anorthositic intrusive yet recognized within the Grenville Province. The Sm-Nd isotopic system records an age of 2377 + or - 68 Ma. High Pb-208/Pb-204 of deformed samples relative to igneous-textured rocks implies Th introduction and/or U loss during metamorphism in the River Valley area. Rb-Sr data from igneous-textured and deformed samples and from mineral separates give an age of 2185 + or - 105 Ma, indicating substantial disturbance of the Rb-Sr isotopic system.
    Keywords: GEOPHYSICS
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 53; 633-641
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  • 64
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    Modeled F region response to auroral dynamics based upon Dynamics Explorer auroral observations (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Auroral images from the Dynamics Explorer 1 (DE 1) scanning auroral imager have been combined with in situ auroral precipitation data from the DE 2 low-altitude plasma instrument, to form a time-dependent global auroral energy flux model. This model has both good time (12 min) and spatial (100 km) resolution compared to that currently available for global-scale ionospheric and thermospheric modeling. The development and comparison of this model with others are discussed. Data from an aurorally active period, November 25, 1981, are presented and used as a case study for this model. Using a global ionospheric model, the effect of the DE auroral model is contrasted with that of a conventional empirical auroral energy flux model. Major differences in the modeled F region ionosphere are predicted from this comparative study.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 8993-900
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  • 65
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    Some low-altitude cusp dependencies on the interplanetary magnetic field (1989)
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    Publication Date: 2019-07-12
    Description: The low-altitude cusp dependencies on the interplanetary magnetic field (IMF) were investigated using the algorithm of Newell and Meng (1988) to identify the cusp proper. The algorithm was applied to 12,569 high-latitude dayside passes of the DMSP F7 spacecraft, and the resulting cusp positioning data were correlated with the IMF. It was found that the cusp latitudinal position correlated reasonably well (0.70) with the Bz component when the IMF had a southward component. The correlation for the northward Bz component was only 0.18, suggestive of a half-wave rectifier effect. The ratio of cusp ion number flux precipitation for Bz southward to that for Bz northward was 1.75 + or - 0.12. The statistical local time widths of the cusp proper for the northward and the southward Bz components were found to be 2.1 h and 2.8 h, respectively.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 8921-892
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    Water vapor and methane in the upper stratosphere - An examination of some of the Nimbus 7 measurements (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The zonal mean volume mixing ratios of water vapor and methane from January to May, 1979, derived from the Nimbus-7 limb IR monitor of the stratosphere and from stratosphere and mesosphere sounder experiments are investigated. The water vapor mixing ratio of air that enters the stratosphere from the troposphere and the yield of water vapor from photochemical oxidation of methane in the stratosphere are examined. The water vapor yield averaged between 1.5 and 2.0, although variability with time and level was relatively large. It is suggested that water vapor yield increases with height in the 16- to 3-mbar range. The average water vapor mixing ratio fo air entering the stratosphere during the study period was about 3.25 X 10 to the -6th.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 8474-848
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    Comparative studies of aerosol extinction measurements made by the SAM II and SAGE II satellite experiments (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Results from the Stratospheric Aerosol Measurement (SAM) II and Stratospheric Aerosol and Gas Experiment (SAGE) II are compared for measurement locations which are coincident in time and space. At 1.0 micron, the SAM II and SAGE II aerosol extinction profiles are similar within their measurement errors. In addition, sunrise and sunset aerosol extinction data at four different wavelengths are compared for occasions when the SAGE II and SAM II measurements are nearly coincident in space and about 12 hours apart.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 8312-842
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    Combining electric field and aurora observations from DE 1 and 2 with ground magnetometer records to estimate ionospheric electromagnetic quantities (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Global distribution of electric fields and currents in the high-latitude ionosphere was estimated using data from the ground-based network of magnetometers and from nearly simultaneous observations with DE 1 and DE 2 satellites. The electric field and current distributions at high altitudes were calculated from instantaneous ionospheric conductivity (estimated from the DE 1 auroral data), using the Kamide et al. (1981) magnetogram inversion technique; an optimum conductivity was then chosen iteratively so that the resultant electric fields would become consistent with electric field deduced from ion drifts measured along the DE-2 orbit. It is demonstrated that, when analyzing the large-scale electrodynamics of individual substorms, statistical conductivity models are not fully adequate for use with the magnetogram inversion technique.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 6723-673
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  • 69
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    Chemical consequences of the initial diffusional growth of cloud droplets - A clean marine case (1989)
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    Publication Date: 2019-07-12
    Description: A simple microphysical cloud parcel model and a simple representation of the background marine aerosol are used to predict the concentrations and compositions of droplets of various sizes near cloud base. The aerosol consists of an externally-mixed ammonium bisulfate accumulation mode and a sea-salt coarse particle mode. The difference in diffusional growth rates between the small and large droplets as well as the differences in composition between the two aerosol modes result in substantial differences in solute concentration and composition with size of droplets in the parcel. The chemistry of individual droplets is not, in general, representative of the bulk (volume-weighted mean) cloud water sample. These differences, calculated to occur early in the parcel's lifetime, should have important consequences for chemical reactions such as aqueous phase sulfate production.
    Keywords: GEOPHYSICS
    Type: Tellus, Series B - Chemical and Physical Meteorology (ISSN 0280-6509); 41B; 51-60
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  • 70
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    The horse-collar aurora - A frequent pattern of the aurora in quiet times (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The frequent appearance of the 'horse-collar aurora' pattern in quiet-time DE 1 images is reported, presenting a two-hour image sequence that displays the basic features and shows that it sometimes evolves toward the theta configuration. There is some evidence for interplanetary magnetic field B(y) influence on the temporal development of the pattern. A preliminary statistical analysis finds the pattern appearing in one-third or more of the image sequences recorded during quiet times.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 16; 37-40
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    Comment on - 'Upstream energetic ions under radial IMF - A critical test of the Fermi model' (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: A criticism is offered by Fusilier of the conclusion by Sarris and Krimigis (SK, 1988) that the failure to observe energetic ions continuously under near radial interplanetary magnetic field conditions contradicts a fundamental prediction of the Fermi mechanism for the origin of the upstream ions. It is argued that both events reported by SK fall short of critical tests of the Fermi mechanism because the magnetic turbulence required by the Fermi process is not guaranteed to be present. Sarris replies that the ad hoc limit on the local angle between the magnetic field and the shock normal imposed by Fusilier is not a relevant consideration to upstream ion activity.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 16; 109-111;
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  • 72
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    Excitation of linearly stable waves in a multispecies plasma (1989)
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    Publication Date: 2019-07-12
    Description: Excitation of electrostatic modes as a result of the injection of an argon beam into a multispecies plasma is investigated. It is shown that the injection of a warm artificial beam into a thermal plasma may excite waves of significant amplitude with a range of phase velocities which are linearly stable. These waves appear as a result of the correlation between motions of an individual particle in a Vlasov fluid. When the free energy is derived from a warm beam and the linear instability diminishes due to the large temperature of the beam, the competing mechanism of thermal fluctuations is responsible for the main excitation of waves. This mechanism is valid for the various modes in a multispecies plasma, with a higher enhancement at the lower-hybrid than at the ion-ion-hybrid modes.
    Keywords: GEOPHYSICS
    Type: IEEE Transactions on Plasma Science (ISSN 0093-3813); 17; 201-204
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  • 73
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    Temporal features of the outflow of heavy ionospheric ions in response to a high altitude plasma cavity (1989)
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    Publication Date: 2019-07-12
    Description: Using a hydrodynamic model for the plasma, it is demonstrated that the auroral plasma cavity is capable of drawing an appreciably large flux of oxygen ions, which are normally gravitationally bound. This escape mechanism of O(+) does not involve any additional heating or acceleration of the plasma in the ionosphere. The temporal evolution of the outflow shows that it starts near the cavity and penetrates into the ionosphere with a flux front moving down with the ion-acoustic speed. A steady outflow is reached in a few hours for a cavity at a height of one R(e) if the cavity is maintained. This time reduces to less than 1 hour for cavity heights less than 3000 km. During the transient state the outflux can appreciably exceed that in the steady state. In view of the horizontal convection, the transient outflow is of special significance. As the cavity descends, the ionospheric flux of O(+) increases; for the lower edge of the cavity in the altitude range 3000-10,000 km, the steady flux is found to be in the range 10 to the 7th to 10 to the 9th. An analysis for the steady state shows that outflow is controlled by the density scale height in the cavity.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 16; 29-32
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    A theoretical interpretation of upstreaming electrons and elevated conics on auroral field lines (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Recent VIKING satellite observations in the auroral zone have shown the association of elevated ion conics (conics with a low energy cutoff above zero) with upward streaming electrons in the presence of low frequency electric field fluctuations. A self-consistent particle simulation was developed which assumed the presence of a steady state electric field on auroral zone field lines capable of accelerating ions up the magnetic field lines. Results from this study show that a low frequency ion-ion two stream instability can be excited. This low frequency instability creates a fluctuating electric field which heats the ions oblique to the magnetic field forming distributions similar to the elevated ion conics. The ion-ion waves also interact resonantly with electrons and accelerates them in the direction of the ion beam.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 16; 21-24
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    The proximity of hotspots to convergent and divergent plate boundaries (1989)
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    Publication Date: 2019-07-12
    Description: An analysis of four different hotspot distributions, ranging from Morgan's (1972) original list of 19 to Vogt's (1981) list of 117 reveals that the hotspots are preferentially located near divergent plate boundaries. The probability of this proximity occurring by chance alone is quite remote, less than 0.01 for all four hotspot distributions. The same analysis also reveals that the hotspots are preferentially excluded from regions near convergent plate boundaries. The probability of this exclusion occurring by chance alone is 0.1 or less for three out of the four distributions examined. We interpret this behavior as being a consequence of the effects of large scale convective circulation on ascending mantle plumes. Mantle thermal plumes, the most probable source of hotspots, arise from instabilities in a basal thermal boundary layer. Plumes are suppressed from regions beneath convergent boundaries by descending flow and are entrained into the upwelling flow beneath spreading centers. Plate-scale convective circulation driven by subduction may also advect mantle thermal plumes toward spreading centers.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 16; 433-436
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    Generation and propagation of kilometric radiation in the auroral plasma cavity (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The two-dimensional particle simulations and three-dimensional ray-tracing calculations presently used to characterize the generation and propagation of EM radiation due to the auroral plasma cavity's electron cyclotron maser instability incorporate a continuous flow of primary energetic electrons along the magnetic field. The magnetic field gradient is found to be unimportant in accounting for various quasi-local properties of the maser instability. The maser instability can produce the observed amplification of auroral kilometric radiation above cosmic background levels within a distance smaller than the dimensions of the auroral cavity.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 129-143
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    Plate tectonics 2.5 billion years ago - Evidence at Kolar, south India (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The Archean Kolar Schist Belt, south India, is a suture zone where two gneiss terranes and at least two amphibolite terranes with distinct histories were accreted. Amphibolites from the eastern and western sides of the schist belt have distinct incompatible element and isotopic characteristics suggesting that their volcanic protoliths were derived from different mantle sources. The amphibolite and gneiss terranes were juxtaposed by horizontal compression and shearing between 2530 and 2420 million years ago (Ma) along a zone marked by the Kolar Schist Belt. This history of accretion of discrete crustal terranes resembles those of Phanerozoic convergent margins and thus suggests that plate tectonics operated on earth by 2500 Ma.
    Keywords: GEOPHYSICS
    Type: Science (ISSN 0036-8075); 243; 1337-134
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    Gravity wave structure between 60 and 90 km inferred from Space Shuttle reentry data (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Density fluctuations obtained along seven Space Shuttle reentry tracks are used to examine the horizontal structure and the vertical distribution of density variance in the mesosphere and lower thermosphere. The tracks lie primarily over open ocean at middle and low latitudes and represent the only measurements of horizontal atmospheric structure at these heights available to date. The density fluctuations are interpreted in terms of gravity-wave motions and reveal significant density (and velocity) variance at horizontal scales ranging from about 10 to 1000 km. Fluctuation amplitudes are used to infer corresponding velocity perturbations and characteristic vertical scales and frequencies of the wave spectrum. Results suggest that the mean velocity variance is smaller over the Pacific ocean than over major land masses, and that the variance increases with height in a manner consistent with that expected in the present of wave saturation processes.
    Keywords: GEOPHYSICS
    Type: Journal of the Atmospheric Sciences (ISSN 0022-4928); 46; 423-434
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    The separated polar winter stratopause - A gravity wave driven climatological feature (1989)
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    Publication Date: 2019-07-12
    Description: An examination of satellite-derived temperatures reveals that the winter polar stratopause is usually elevated and warmer than the adjacent midlatitude stratopause. This separated stratopause occurs in both hemispheres, but is more pronounced and persistent in the southern winter. It descends with time towards spring and exhibits week-to-week variability. Observational diagnostics and results from a two-dimensional model suggest that gravity-wave driving can account for this separated polar stratopause by driving a meridional circulation, with downwelling over the winter pole. In the model, the solar heating pattern induces stronger winter westerlies than summer easterlies, which leads to a stronger gravity-wave-driven circulation in the winter hemisphere. Spherical geometry and the high latitude location of the winter westerly jet combine to yield a concentrated region of downwelling. Model results suggest that descent of the temperature maximum with time is probably caused by wave/mean-flow interaction.
    Keywords: GEOPHYSICS
    Type: Journal of the Atmospheric Sciences (ISSN 0022-4928); 46; 410-422
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    Stability of H(+) beams in the polar wind (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The effect of energetic H(+) beams on the stability of the polar wind in the classical model is studied with regard to the excitation of electrostatic waves. Consideration is given to cases covering a wide range of electron-to-background temperature ratios and beam-to-background ion density ratios, assuming a relatively cold beam. The minimum beam drift velocity required to destabilize the plasma is determined by a combination of the Nyquist technique and a direct solution of the plasma dispersion equation. It is found that the plasma can be destabilized for relative drift energies less than about 1 eV. Also, it is shown that the plasma is less stable for large electron temperatures and for comparable ion and beam densities.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 1487-149
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    Excitation of low-frequency waves by auroral electron beams (1989)
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    Publication Date: 2019-07-12
    Description: The electron distribution functions measured by the Dynamics Explorer 1 satellite during an auroral pass in 1981 are used in a linear instability analysis of low-frequency electromagnetic and electrostatic waves near and below the hydrogen gyrofrequency. It is suggested that the low-frequency electric and magnetic noise in the auroral zone might be explained by O and H electromagnetic ion cyclotron waves excited by energetic electron beams. An instability analysis suggests that upward and downward streaming electrons throughout the central plasma sheet region provide the free energy for heating oxygen ion through oxygen electrostatic ion cyclotron waves.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 1327-133
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    Steady state magnetic field configurations for the earth's magnetotail (1989)
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    Publication Date: 2019-07-12
    Description: A two-dimensional, force-balance magnetic field model is presented. The theoretical existence of a steady state magnetic field configuration that is force-balanced and consistent with slow, lossless, adiabatic, earthward convection within the limit of the ideal MHD is demonstrated. A numerical solution is obtained for a two-dimensional magnetosphere with a rectangular magnetopause and nonflaring tail. The results are consistent with the convection time sequences reported by Erickson (1985).
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 1303-131
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    NH3 column abundances over Lauder, New Zealand (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Gaseous NH3 has been observed in the atmosphere over central New Zealand with infrared absorption spectra. The amount of NH3 shows marked variability, which is strongly correlated with time of day and season. The pattern is similar to data obtained in Denver, Colorado, but is much more variable than data from Hampton, Virginia. The rapid variability indicates a residence time of 8 hours in some cases.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 2235-223
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    Simulations relevant to the beam instability in the foreshock (1989)
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    Publication Date: 2019-07-12
    Description: The results presently obtained from two-dimensional simulations of the reactive instability for Maxwellian beams and cutoff distributions are noted to be consistent with recent suggestions that electrons backstreaming into earth's foreshock have steep-sided cutoff distributions, which are initially unstable to the reactive instability, and that the back-reaction to the wave growth causes the instability to pass into its kinetic phase. It is demonstrated that the reactive instability is a bunching instability, and that the reactive instability saturates and passes over into the kinetic phase by particle trapping.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 79-88
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    A magnetohydrodynamic simulation of the formation of magnetic flux tubes at the earth's dayside magnetopause (1989)
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    Publication Date: 2019-07-12
    Description: Dayside magnetic reconnection was studied by using a three-dimensional global magnetohydrodynamic simulation of the interaction between the solar wind and the magnetosphere. Two different mechanisms were found for the formation of magnetic flux tubes at the dayside magnetopause, which depend on the orientation of the interplanetary magnetic field (IMF). The dayside magnetic flux tubes occur only when the IMF has a southward component. A strongly twisted and localized magnetic flux tube similar to magnetic flux ropes appears at the subsolar magnetopause when the IMF has a large B(y) component. When the B(y) component is small, twin flux tubes appear at the dayside magnetopause. Both types of magnetic flux tube are consistent with several observational features of flux transfer events and are generated by antiparallel magnetic reconnection.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 16; 155-158
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  • 86
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    Trapped-particle evacuation - Source of magnetotail bursts and tailward flows? (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Observational and theoretical evidence that the polar cap can expand rapidly enough during the growth phase of a substorm to release geomagnetically trapped particles from previously closed drift shells, enabling the particles to escape into the tail, are examined. Observations show that the moving separatrix can overtake convecting nightside plasma during intervals of polar-cap expansion. Models of this phenomenon suggest that closed nightside field lines can be evaculated of their particle populations, and it is noted that such evacuations can account for the occurrence of energetic-particle bursts in the tail.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 16; 353-356
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  • 87
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    Effects of ion two-stream instability on auroral ion heating (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The ion two-stream instability develops between upflowing H(+) and O(+) in the auroral acceleration region, if the two species are accelerated to different velocities in a semistationary electrostatic potential. Parallel propagating modes are unstable only for small relative drifts, while oblique modes remain unstable at larger drifts and, consequently, higher altitudes. The effects of oblique modes on ion heating are investigated, and it is found that O(+) heats primarily by trapping in the direction of wave propagation during the early, coherent phase of wave growth in the temporal evolution problem. After undergoing trapping along the magnetic field direction, H(+) heats primarily by quasi-linear diffusion when the spectrum broadens nonlinearly. The parallel ion distributions evolve by formation of a high-energy (low-energy) tail on oxygen (hydrogen) along with bulk slowing of hydrogen, which results in more energetic oxygen than hydrogen. Total heating is greatest in the direction of wave propagation, and this effect is greater for hydrogen than for oxygen.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 348-358
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  • 88
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    Mapping of the solar wind electric field on the earth's polar caps (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: A quantitative model of a magnetically interconnected (open) magnetosphere is developed as a perturbation of Voight's closed magnetosphere model with a given magnetopause shape. The model is shown to give a reasonable representation of the open magnetosphere configuration and is especially useful in testing the magnetospheric consequences of various merging theories. The convection pattern obtained for southward IMF is in reasonable agreement with observations, especially in the manifestation of a convection 'throat' near noon. For northward IMF, this region of constricted flow is rotated in local time in the direction of the IMF, also in accordance with observations.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 329-347
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  • 89
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    Three-dimensional equilibria for the extended magnetotail and the generation of field-aligned current sheets (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Using the magnetotail equilibrium theory and a solution method outlined by Birn (1987), self-consistent three-dimensional models were constructed for the quiet average magnetotail beyond about 20 RE distance but earthward of a potential distant neutral line, which take into account the decrease of the tail flaring with distance. It is found that this effect is coupled with the presence of magnetic shear and thus with field-aligned electric currents. These currents have the signature of region 1 currents, toward the earth on the dawnside and away on the duskside, and contribute about 500,000 A to the total Birkeland current.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 252-260
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  • 90
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    Filamentary structure of a three-dimensional plasmoid (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The changes of the magnetic field topology and the field line connections are examined in detail using a simple explicit magnetic field model of a plasmoid in different stages from its formation, penetration through a separatrix connected with a distant neutral line, to its complete disconnection. It is shown that complications arise from the fact that separatrix surfaces become very complicated, folded, and filamented in the presence of a small but finite magnetic field in the reconnection region. The filamentary mixing of topologically different field lines may lead to a mixing of different plasma populations as well, and thereby possibly to a more efficient dissipation.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 241-251
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  • 91
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    Time-dependent convection with non-Newtonian viscosity (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: A numerical model of bottom-heated, two-dimensional convection in boxes of aspect ratios 2.5 and 4.0 was used to study the differences in time-dependent convection between Newtonian and stress-dependent viscosity. The onset of time dependence due to boundary layer instability is found at approximately the same effective Rayleigh number for both rheologies. However, with increasing Rayleigh number, the temporal and spatial fluctuations in the flow field become much more pronounced with non-Newtonian rheology; also, the tendency for breakup of long cells into smaller ones is stronger. The presence of stress-dependent rheology can cause long-wavelength lateral viscosity variations up to an order of magnitude; this result could have strong implications for the interpretation of mantle viscosity from postglacial rebound.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 814-820
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  • 92
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    Platinum group elements in a 3.5 Ga nickel-iron occurrence - Possible evidence of a deep mantle origin (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: This paper reports the results of new field observations and the geochemical analyses for the area of the Bon Accord (BA) (the Kaapvaal craton, South Africa) Ni-Fe deposit, with particular consideration given to the trace element, platinum-group element, and isotopic (Pb, Nd, and Os) compositions. On the basis of these data, an interpretation of BA is suggested, according to which the BA deposit is a siderophile-rich heterogeneity remaining in the deep mantle after a process of incomplete core formation. The implications of such a model for the study of core-mantle segregation and the geochemistry of the lowermost mantle are discussed.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 795-813
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  • 93
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    Solar radiative transfer in cirrus clouds. I - Single-scattering and optical properties of hexagonal ice crystals. II - Theory and computations of multiple scattering in an anisotropic medium (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The light scattering and absorption programs of Cai and Liou (1982) and Takano and Jaweera (1985) are extended to include hexagonal ice crystals randomly and horizontally oriented in space. The scattering and polarization results for the ice crystals are calculated. The results are compared with measurement data. The single-scattering properties for horizontally oriented columns and plates are presented and used to explain halos and arcs observed in the atmopshere. In the second section, the theory and computations for multiple scattering in cirrus clouds containing oriented ice crystals are presented. The radiative transfer in clouds composed of horizontally oriented ice crystals is formulated. Also, reflected and transmitted intensities, planetary albedo, and polarization in multiple scattering by ice crystals are discussed.
    Keywords: GEOPHYSICS
    Type: Journal of the Atmospheric Sciences (ISSN 0022-4928); 46; 3-36
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  • 94
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    On the effect of a tangential discontinuity on ions specularly reflected at an oblique shock (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: A study is conducted for the case of a tangential discontinuity (TD) that convects into a shock at some arbitrary angle, in order to clarify events observed in proximity to the earth's bow shock. Very different behavior is noted to result depending on the sense of ion gyration relative to the TD. The fact that particles can be injected into the TD's plane, so that they travel upstream close to the TD, implies that active current sheet (ACS) events thus far assumed to be generated by the solar wind's interaction with a large-density reflected component are actually detached from the bow shock. In other geometries, ions stay close to the shock after their TD interaction, implying that ACS events are modifications of the shock.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 472-478
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  • 95
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    Particle distributions in a two-dimensional reconnection field geometry (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: In order to understand space phase density variations near the magnetopause and in the geomagnetic tail, particle trajectories in a two-dimensional steady state reconnection field geometry are studied by tracing particles from a spacecraft position back in time. The distribution function at the spacecraft is calculated using Liouville's theorem and known distribution functions in the source regions. It is found, in particular, that multiple ion beams in the plasma sheet boundary layer are a natural consequence of reconnection. In the center of the central plasma sheet, the omnidirectional flux of keV ions should be at a minimum. The depth of this minimum is very large near the neutral point but decreases as the distance from the neutral point increases.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 272-286
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  • 96
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    Time-dependent modeling of field-aligned current-generated ion transients in the polar wind (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The time evolution of field-aligned current-generated transient features in the high-latitude ionosphere is investigated. Ionospheric return currents generate significant downward heavy ion flows in the topside ionosphere with peak values well exceeding 10 to the 8th sq cm/s. When the return current ceases, the polar ionosphere rapidly returns to its previous equilibrium state. During the recovery phase of the return current event, an upward propagating heavy ion transient is formed, which is mainly characterized by a relatively short O(+) upwelling event. On the other hand, the H(+) escape flux remains relatively constant (within 10-20 percent) during field-aligned current events. It is also found that upward currents generate a transient heavy ion outflow, which exceeds the ambient H(+) escape flux by a factor of 3 to 5, depending on the duration and strength of the field-aligned current event.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 359-369
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  • 97
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    Shock temperatures in silica glass - Implications for modes of shock-induced deformation, phase transformation, and melting with pressure (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Observations of shock-induced radiative thermal emissions are used to determine the gray body temperatures and emittances of silica glass under shock compression between 10 and 30 GPa. The results suggest that fused quartz deforms heterogeneously in this shock pressure range. It is shown that the 10-16 GPa range coincides with the permanent densification region, while the 16-30 GPa range coincides with the inferred mixed phase region along the silica glass Hugoniot. Low emittances in the mixed phase region are thought to represent the melting temperature of the high-pressure phase, stishovite. Also, consideration is given to the effects of pressure on melting relations for the system SiO2-Mg2SiO4.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 5851-587
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  • 98
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    Comment on 'Observations of Low-Latitude Electron Precipitation' by R. Lieu, J. Watermann, K. Wilhelm, J. J. Quenby, and W. I. Axford (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Observations made by an electron spectrometer aboard Spacelab 1 and presented by Lieu et al. (1988) are examined critically. The precipitation of electrons in the energy range of 0.1-12.5 keV was measured on December 6 and 7, 1983. Data for 16 passes near 240 km altitude, between + and - 30 deg geographic latitude, outside the South Atlantic Anomaly were included. It is argued that there is no geophysical confirmation of the large electron fluxes reported by Lieu et al. In their response, Lieu et al. discuss the sampling bias in the Spacelab 1 data and the magnetic shielding deficiencies of the calibration facility below about 500 eV.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 9155-915
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  • 99
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    Collisional and inertial dynamics of the ionospheric interchange instability (1989)
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    Publication Date: 2019-07-12
    Description: The dynamical properties and spectral characteristics of the ionospheric interchange instability in the collisional and inertial regimes are investigated numerically and analytically, using a two-dimensional fluid model. This model, which describes the collisional and inertial dynamics of the F region ionosphere, is similar to the models of Ott (1978) and Kintner and Seyler (1985). By numerically integrating the model equations, the nonlinear evolution of three interchange unstable configurations in the collisional and inertial regimes are followed, and their dynamical and spectral properties are studied. The solutions indicate that the dynamical properties of a collision-dominated regime are distinctly different from those of an inertia-dominated regime. The qualitative characteristics of a plasma bubble in both regime-types are described.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 9009-902
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  • 100
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    Simulations and observations of heating of auroral ion beams (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Two-dimensional three-velocity electrostatic particle simulations were used to determine the nonlinear evolution of the distributions of auroral ion beams and thereby to determine quantitatively signatures in the ion distributions produced by the ion-ion instability for a variety of plasma conditions in the auroral zone. The signatures determined from these simulations were compared with observations from DE 1, making it possible to characterize semiquantitatively the heating of the ionospheric ions, and to investigate the causes of variability seen in the observations of Reiff et al. (1988). A comparison of the simulation with observations showed features consistent with heating via the ion-ion instability including perpendicular heating in the supersonic regime and parallel heating in the subsonic regime, and a change in the heating between these regimes as the ratio of the H(+) beam speed to the local sound speed decreases.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 8943-896
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